Shader "Custom/FrostedGlass"
{
    Properties
    {
        _FrostTex ("Fross Texture", 2D) = "white" {}
        _FrostIntensity ("Frost Intensity", Range(0.0, 1.0)) = 0.5
        _Color ("Color", Color) = (1,1,1,1)

    }
    SubShader
    {
        Tags { "RenderType"="Transparent" "Queue" = "Transparent" }
        LOD 100

        Pass
        {
            CGPROGRAM
            #pragma vertex vert
            #pragma fragment frag
            
            #include "UnityCG.cginc"

            struct appdata
            {
                float4 vertex : POSITION;
                float2 uv : TEXCOORD0;
            };

            struct v2f
            {
                float2 uvfrost : TEXCOORD0;
                float4 uvgrab : TEXCOORD1;  
                float4 vertex : SV_POSITION;
            };

            sampler2D _FrostTex;
            float4 _FrostTex_ST;
            fixed4 _Color;

            float _FrostIntensity;

            sampler2D _GrabBlurTexture_0;
            sampler2D _GrabBlurTexture_1;
            sampler2D _GrabBlurTexture_2;
            sampler2D _GrabBlurTexture_3;
            
            v2f vert (appdata v)
            {
                v2f o;
                o.vertex = UnityObjectToClipPos(v.vertex);
                o.uvfrost = TRANSFORM_TEX(v.uv, _FrostTex);
                o.uvgrab = ComputeGrabScreenPos(o.vertex);
                return o;
            }
            
            fixed4 frag (v2f i) : SV_Target
            {
                float surfSmooth = 1-tex2D(_FrostTex, i.uvfrost) * _FrostIntensity;
                
                surfSmooth = clamp(0, 1, surfSmooth);

                half4 refraction;

                half4 ref00 = tex2Dproj(_GrabBlurTexture_0, i.uvgrab);
                half4 ref01 = tex2Dproj(_GrabBlurTexture_1, i.uvgrab);
                half4 ref02 = tex2Dproj(_GrabBlurTexture_2, i.uvgrab);
                half4 ref03 = tex2Dproj(_GrabBlurTexture_3, i.uvgrab);

                float step00 = smoothstep(0.75, 1.00, surfSmooth);
                float step01 = smoothstep(0.5, 0.75, surfSmooth);
                float step02 = smoothstep(0.05, 0.5, surfSmooth);
                float step03 = smoothstep(0.00, 0.05, surfSmooth);

                refraction = lerp(ref03, lerp( lerp( lerp(ref03, ref02, step02), ref01, step01), ref00, step00), step03);
                
                return refraction*_Color;
            }
            ENDCG
        }
    }
}